<div class="content">
				<div class="row main-row">
					<div class="col-md-2 nav">
							<nav>                             <!--$nav_part是修饰当前导航栏标题背景颜色的CSS语句-->
								<div class="instrument" <?= $nav_index ?>><h1 class="text-center"><a href="index.php">仪表盘</a></h1></div>
								<div class="article" <?= $nav_article ?>><h1 class="text-center"><a href="article.php?page=1">文章</a></h1></div>
								<div class="link" <?= $nav_link ?>><h1 class="text-center"><a href="link.php">链接设置</a></h1></div>
								<div class="exit"><h1 class="text-center"><a href="login.php">退出登录</a></h1></div>
							</nav>
					</div>